Electrical resistance alloys



ELECTRICAL nnsrsrarscn ALLOYS Patented Sept. 2, 1958 ice sistance elements possessing these valuable properties, which are especially suitable for use in precision instrumentation, such as in electrical and electronic control devices.

Carrol Dean Starr, Whippany, and James E. Daly, 5 We have discovered that the objects of this invention Colonia, N. 3., assignors to Wilbur B. Driver Comcan be achieved by the provision and utilization of alloy P Newark, a p Of New Jersey compositions consisting essentially of fi-om 2 to 4.5% No Drawing. Application September 26, 1956 gt Al, 2 to 8% of V and 15 to 25% of Cr in a nickel Serial No. 012,108 10 Ni-Cr type alloys of this formulatlon possess valuable 7 Claims- (C 75 properties of corrosion resistance, strength and ductility similar to those of known electrical resistance alloys of This invention relates to electrical resistance alloys of the nickel-chromium type. Being both hot workable the nickel-chromium type and to resistance elements made and cold workable, they can be readily converted from of these alloys, which are particularly suitable for use ingot form into the form of fine resistance elements, in electrical or electronic control devices. such as wires, ribbons or other pliable strands. We have Nickel-chromium electrical resistance alloys are comfurther discovered, however, that when these alloys are monly made with a base composed of Ni and from 10 suitably annealed and heat-treated, the products obtained to 30% of Cr. The resistivity and the temperature have an extraordinarily high resistivity of at least 950 coeflicient (T. C.) of products made of these alloys, ohms per circular mil foot, and their temperature cosuch as wires, ribbons or other pliable strands, are propelficient of resistance is so small that it departs from erties of great importance to the usefulness of the prodzero, if at all, by not more than about .000020 ohms nets in electrical or electronic control devices, such as per ohm per degree C. over the temperature range of 20 resistors, otentiometers and the like. to 100 C.

A typical alloy of 80% Ni and 20% Cr, when drawn Illustrative examples of the alloys and resistance eleinto fine wire and subsequently strand annealed, shows ments of this invention are set forth in Table I hereof. a resistivity of approximately 612 ohms per circular mil As to each example, this table shows the weight perfoot (C. M. F.) and a temperature coeflicient of recentage of the essential alloy ingredients, as determined sistance of about .00018 ohms per ohm per degree centiby chemical analyses, the important resistance properties grade over the temperature range of 20 to 100 C. of heat treated .0253" Wire strands made of the alloy, When suitably heat treated, its resistivity rises to about and the conditions of heat treatment. The strands had 650 ohms/C. M. F., and its temperature coefficient is been annealed at 1750 F. to 2150 F. in a 12 foot reduced to about .00009 ohms/ohm/ C. furnace at a speed of 42 ft./min., cooled rapidly and It is known that the reistivity of such alloys may be then heat treated in a reducing atmosphere of cracked substantially increased by adding to a nickel-chromium ammonia at the temperatures and for the times listed base suitable amounts of certain alloying elements, parin Table I. All the alloys contained as incidental eleticularly Si, Mn and Fe, V and Fe, Mn, V and Fe, Cu ments very small amounts of C, Ca, Co, Fe, Mg, Pb, Si and Al, or Cu, Al and Fe. When suitably fabricated, and Zr. strand annealed and heat treated, some of the resulting When the aluminum content of compositions like those compositions show a very low temperature coefficient of Table I is increased above 4.5%, the resistivity of that varies from zero by not more than about .000020 heat treated strands of the alloys still reaches approxiohms per ohm per degree C. mately 1000 ohms/C. M. F., but there is an inordinate As far as we are aware, however, there is no known increase of the temperature coeflicient which makes the composition of a Ni-Cr type alloy that can be processed products unsuitable for the requirements of fine electrical commercially into electrical resistance elements having resistance elements. When the vanadium content is inhoth a very low temperature coeflicient of the order stated creased above 8.0%, the compositions no longer have above and a resistivity as high as approximately 1000 the desired ductility and working properties. When ohms per C. M. F. Yet products of that character are either the aluminum content or the vanadium content is highly desirable for a variety of electrical and electronic 5O reduced below the required gh resistivity is not uses. attained.

t is the principal object of this invention to provide While the processing or" the present alloys into realloys which can be converted readily into electrical sistance elements may be carried out in a variety of resistance elements having both a very low temperature known ways, the following is one suitable procedure coeiiicient of resistance and an extraordinarily high rewhich has been employed in processing the examples sistivity. Another object is to provide fine electrical rereferred to herein.

Table I Heat treated strands Strand Heat Time of Example Per- Per- Percent Percent anneal treat heat cent Al cent 'v' Cr Ni temp, temp, treat, Resistivity, T. 0., tZ/QPC.

F. F. hours ohms/ (ZS-100 C.)

Nickel and chromium in mately 4:1, together with the other essential ingredients of the composition, are melted together in an electric induction jfurnace." The *fmelt :usually contains .minor,

a weight ratio of approxi-..

2.5% titanium may be added ,in amounts up to about 3.5%; tungsten may be added in amounts up to about 2%; and arsenic or beryllium may be added in amounts up to about .25%-in each case, while retaining the about 5%; silicon may be added in amounts'up toabout amounts ofincidental elementsiirthenature of impurities 5 required workability of the alloys as well as their capacity or degasifying elements, such as C, Ca, Ce, Co,Cu,:Fe, to form electrical resistance elements havingthe distinc- Mg, Mn, Pb, Si and/or Zr. The melt is castinto ingots tive properties described herein. Table II hereof gives which are heated atabout 2250 F; 1901730 to 45 minillustrative examples of alloy compositions embodying r tes and then are=hotrolledtorod form. .Therods are this invention which contain'some of, such minoraddinormalized forflihrnat 2l50 =.F., thencoated with'a'suittions, and shows theresistance properties of heat treated able'die lubricant, isuch: asby dipping them'in a bath .0253 inch wire strands made of the modified alloys.

Table II 1 i p Heat treated strands I V V Cu Fe lvin Si iiirie i ai E221? i e a t I V Eianrlple Base A1 temp, temp, v treat, I g l T.C.,Sl/11/O.

r. 1 hoursf f (-100C.)

3:70 4.80 5.37 1,750 1,000 32 1,005 0.0oo01s 4.08 4:00 2.8 2,100 1; 100 4 1, 04s -o.0o001s 3. 77 4.00 0. 72 1, 750 1,100 1% 982 1 o of rn0lten 'lead, and-then cold" drawn through dies to The principlesof this invention and preferred-ways the desired strand "size." iThe cold I drawing is effected of putting it into practice having-been described hereinin stages' with intermediate steps of annealing at 1750 H above, its essential features "which we intendto secure to 2250 8, pickling, and rewoating with lead. "The by Letters Patent are set forth in the following claims. final strands may be Wires as fine as .001 inch, or even We claim: smaller, in'diameter; 1. An electrical resistance -alloy consisting essentially The drawn-strands are givena final anneal at 1750 3O offroml to 4.5% -of Al, 2'to-8% of V and 15 t0-25% to 2150 F. in a12 foot furnace at 42 ft./min. and of Cr in a Ni base. 1 then cooled rapidly, after which their full resistance 2L An electric'alresistance alloy consisting essentially properties are developed by heating them in a reducing of-from'Zto 45% Al, 2.5 to 7.5% V, 16.5 to 22% Cr' atmosphere, such as one of hydrogen or cracked ammonia, and '67 to 76%-Ni.

at 900'to 1300? F,- for /2 to 100 hours. In general, it 3. An electrical resistance alloy consisting essentially has been found that a higher strand annealtemperature' of from 2 to 4.5 -Al, 3.5 to 7% V,16.5 to 22% Cr permits theme of a lower heat treating'temperature or and 69 to 75% Ni.

a 'shor'ter'time'of heat treatment within these ranges. For 4. An electrical resistance alloy consisting essentially anygiven strand anneal temperature, the higher the heat of from 2.5 -to 4.5% of A1, 3.5. to 6% V, 19 to 21% Cr treating temperature, 'the shorter is the time necessary to and 67 to 76% Ni. 7 obtain the desired electrical properties. i-An electrical resistance alloy consisting ofg ap When a composition is described or claimed herein proximately, 35 to 4% "A1, 4.5 to 5.5% V, 19 to--2l%' as consisting essentially of named elements-in-stated Cr a11d 67to 76%"Ni, with nominal amounts of inciproportions, this expression is intended to mean that dental elements-from theg-roup' consisting of C, a,' Ge, the elementsso specified are the essential ingredients of Co,-Cu-, Fe,Mg,' Mn; Pb, Sifand Zr. 1 the alloy composition, but it is not intended to exclude 6. An electrical resistance alloy consisting of, approxithe presence of minor amounts ofvarious incidental mately, 25% Al, 7% 'V,'19 to 21%(31' and-6710 76% elements inthe nature'of usual deoxidizing elements or Ni,=withnominal amounts of incidental elements from impurities, such as-C, Ca, Ce, Co, C11,Fe, Mg, Mn, the groupconsisting oflC,'Ca, Ce,Co, 011,'Fc, Mg;-Mn, Pb, Si'- a'nd Zr".' Such'elements" commonly are found in Pb,'Si and Zr; 5 the alloys as fa result of-the origin or the method of 7. Anelectrical'resistance element comprising'a pliable preparation of one or more of their essential ingredients. strand of an alloyconsisting essentially of from "2 to Neither is said expressionintended to exclude the possible 4.5% A1, 2 to 8% V and 15 to'25'% -'Cr in a Ni base, addition to the same composition of minor amounts of said strand having a resistivity. of at least "950 elements which areknownto be compatible with'elecohms/C. and a temperature 'coefiicient that does trical resistance alloys ofithe nickel-chromium type, to not vary from zero by more than .000020 ohms/ohm/ the extent that such additions'donot deprive theproducts C, over th range, of 20 r0100 (3, of the valu'ableiresistance properties-specified herein; g V a r i For example, copper may be added -to' the- Present al- JReferences Cited in the f this patent loys in amounts up to about 5% 11011 or cobalt may be added to them in amounts up to 5%, or in somewhat UNITED STATES PATENTS larger amounts 11p to 10% if added at the expense of nickel; manganese may be added in amounts up to 1,803,468 D iver et a1. May 5, 1931 2,460,590 Lohr Feb. 1, 1949 

1. AN ELECTRICAL RESISTANCE ALLOY CONSISTING ESSENTIALLY OF FROM 2 TO 4.5% OF A1, 2 TO 8% OF V AND 15 TO 25% OF CR IN A NI BASE. 